1. Field of the Invention
The present invention relates to emission-gated electron-beam devices and more particularly to devices including an active electronically steered cathode for generating one or more electron beams that are electronically steered at their points of origin.
2. Description of Related Art
In a conventional density-modulated device, such as an inductive output tube (IOT), radio-frequency (RF) gating of electron emission is accomplished using an input cavity structure that develops a peak electric field between the cathode surface and a control grid. By biasing the control grid with respect to the cathode, the cathode can be made to emit electrons during part of the RF cycle. As a result, the electron beam is modulated at the RF drive frequency.
In some applications, it is desirable to generate a helical or deflection-modulated beam. Conventionally, such a beam is generated using bending fields that operate on the electron beam to deflect its trajectory. However, applying bending fields tends to degrade the quality of the electron beam, making it unsuitable in applications that require precise control of the beam trajectory, such as in high-frequency devices where circuit dimensions and geometries are small. In addition, because voltage ripple may cause positional deviations, exceedingly tight power-supply regulation that is difficult to achieve may be required in many applications. Accordingly, it would be desirable to provide an apparatus and method for generating an electronically steered electron beam that overcomes these and other drawbacks of the prior art.